QMMM Calculations

Other examples of C-H H-M short contacts [44] were found in iridium complexes, and the competition between agostic interactions and hydrogen bonds was tested by QMMM calculations for several R groups hanging from an orthometallated benzoquinoline ligand. The agostic structure is favored for t-Bu, but the hydrogen bond is preferred by isopropyl [44b]. 

Molecular mechanics calculations have become a well established tool in the area of coordination chemistry, including the coordination chemistry of nickel375-379 where they are often applied for the analysis or the prediction of structures,380 the computation of isomer or conformer ratios and metal ion selectivities,381,382 and for simulating spectroscopic properties in combination with AOM calculations or by hybrid quantum mechanics/molecular mechanics (QMMM) methods.383,384 Details of the various approaches, e.g., the incorporation of d-electron stabilization energy... 

Mercer IP, Gould IR, Klug DR. Optical properties of solvated molecules calculated by a QMMM method. Faraday Discuss 1997 108 51-62. 

The following results stem from DFT calculations on model rhodium complexes. Based on these model system transition states, force-field calculations were carried out in order to incorporate steric effects. The global energy minima of the new systems were searched for by MD simulations (cf. Section 3.1.2.1). This QMMM method with frozen reaction centers (FRC) is related to approaches recently discussed in the literature [29] cf. [23] for more details. 

Numerical methods. Quantum mechanical calculations, molecular mechanics, and distance geometry (DG) are summarized under numerical methods because they are based on extensive numerical optimization procedures often requiring substantial computation times (QMMM > DG). Although quantum mechanical or molecular mechanics programs need a reasonable starting... 

---